JPS63956A - Luminous device - Google Patents

Abstract

PURPOSE:To prevent the variation of light quantity and to stablize the luminous device, by arranging the lowest temperature part at the position projecting from the discharge tube and the position lower than the discharge starting level. CONSTITUTION:A phosphor is spread in a slender form glass tube, a discharge starting member such as mercury and an inert gas such as Ar are sealed, and moreover, a coil-form electrode 2 is furnished to compose a discharge tube 1. Then, a high-frequency voltage is applied to the electrode 2 from a high-frequency applying device 3 to discharge to get a radiation. In this case, a projection 4 is arranged to be the coolest part 41 at the part of the glass tube end, where the intensity of the high-frequency electromagnetic field is lower than the discharge starting intensity. By controlling the temperature with a temperature control device 5, the variation of the saturated vapor pressure of the mercury is controlled. Therefore, as well as the quanty of the light is stabilized, a luminous device of a high brightness and a long service life can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention generally relates to a lighting device that can be used for various purposes, and in particular to a document reading device that illuminates a document and reads a document image in office equipment, etc. In other words, the present invention relates to an illumination device that can be suitably used as an exposure means or the like.

(Background Art) Conventionally, long lamps (
As elongated light sources, elongated fluorescent lamps, halogen lamps, and the like are frequently used.

Fluorescent lamps have a small amount of light and are usually used as lighting devices for low-speed office equipment.In order to use fluorescent lamps as lighting devices for high-speed office equipment, which is currently in demand, the power supply has been increased. By increasing the brightness (amount of light emitted),
Since the internal filament installed inside the fluorescent tube melts, there is a limit to how much power can be supplied, and in reality, it is unsuitable as a lighting device for high-speed office equipment.

On the other hand, halogen lamps emit a large amount of light and are used for high-speed office equipment, but they emit more light in the infrared range than the visible light range required for reading documents in office equipment. Not only is the luminous efficiency low, but the heat generated by such wavelengths is large, and in order to reduce this heat generation effect, a cooling device, especially a large cooling device, is required. It cannot be said that it is a desirable lighting device in today's world.

The present applicant has proposed an elongated illumination device which solves the drawbacks of the conventional fluorescent lamps and halogen lamps and is suitable not only for general illumination but also particularly for document reading devices for office equipment (Japanese Patent Application No. 1986- No. 78782).

As shown in FIG. 3, the lighting device includes a discharge tube 1a that emits light by a high-frequency electromagnetic field, an electrode 2a disposed on the outer wall of the discharge tube, and a high-frequency applying means for applying a high frequency to the electrode. 3.

To explain further, in FIG. 3, the discharge tube 1a is formed by coating a phosphor inside an elongated glass tube, usually made of soda glass or pyrex glass, and containing mercury or the like inside the discharge tube. A discharge initiating material and an inert gas such as Ar are sealed. Furthermore, electrodes 2a made of a conductive material, such as copper or stainless steel, which are less likely to be oxidized, are arranged at or near both ends of the discharge tube 1a. Although the electrode can be provided slightly apart from the outer wall of the discharge tube, it is usually preferable to provide the electrode in close contact with the outer wall of the discharge tube because the power loss applied to the discharge tube is small.

A high frequency voltage is applied to the electrode 2a by a high frequency applying means 3. When a high frequency voltage is applied to the electrode 2a from the high frequency applying means 3, the mercury gas within the discharge tube is excited by the high frequency electromagnetic field and generates ultraviolet rays. The ultraviolet rays act on the phosphor coated on the inner wall of the discharge tube to generate light in the visible light range.

FIG. 4 shows another embodiment of the illumination device, which differs from the illumination device of FIG. 3 in the structure of the electrodes. In other words, the electrode 2 of this example is wound in a coil shape multiple times along the longitudinal direction of the elongated discharge tube 1a, which has the same configuration as the discharge tube 1a described in connection with FIG. The difference is that the electrode 2 is provided on the outer wall of the discharge tube 1a, and a high frequency voltage is applied to the electrode 2 by a high frequency applying means 3.

The illumination device shown in FIG. 4 is characterized by being able to apply a larger amount of power to the electrodes and obtain a larger amount of light than the illumination device shown in FIG. 3. This is preferable for things that require a large amount of light.

In the lighting device shown in FIGS. 3 and 4 above, the electrodes 2 and 2a are provided outside the discharge tube, and unlike conventional fluorescent lamps and halogen lamps, the lighting device does not have a filament inside the discharge tube. First, the degree of deterioration of the electrodes is extremely small, and the electrodes can be replaced once they have deteriorated, making it possible to always obtain a desired level of brightness (light amount). Furthermore, such a lighting device can apply a large amount of power to the electrodes, making it possible to increase the amount of light.

On the other hand, in this lighting device, the light emission source is ultraviolet light emission due to the excitation of a discharge initiator such as mercury in the discharge tube, so the luminous efficiency fluctuates due to a change in the ultraviolet light emission efficiency due to a change in the vapor pressure of the discharge initiator gas.

The ultraviolet light emission efficiency peaks near the discharge tube wall temperature of 30 DEG to 50 DEG, and decreases as the temperature increases due to an increase in saturated water vapor pressure due to the temperature of the discharge starter gas. For the above reasons, it has been confirmed that in this lighting device, the amount of light emitted decreases as the temperature of the discharge tube increases due to the high-frequency electromagnetic field, and the amount of light decreases when the lighting device is turned on for a long time. That is, when the temperature of the discharge tube changes, the amount of light emitted changes.

(Object of the invention) The present invention is a high-intensity, long-life lighting device that
The purpose of the present invention is to provide a lighting device that can provide a stable amount of light without any fluctuation.

(Summary of the invention) The present invention is a claim that achieves the above object.

(Example of the invention) FIG. 1 shows a schematic configuration of a lighting device according to an embodiment of the present invention.

The discharge tube 1 of the present device is generally made of soda glass or virex glass and has a diameter of 5 to 30 mm and a length of 300 mm, substantially as described in connection with FIG.
The discharge tube is formed by coating a phosphor inside an elongated glass tube, but unlike the discharge tube shown in FIG. 3, it has a coldest point part 41. Inside the discharge tube, a discharge starting material such as mercury and an ionizable starting inert gas such as Ar are sealed at several Torr.

Further, the electrode 2 is arranged in the form of a conductor wire wound in a coil shape a plurality of times along the longitudinal direction of the discharge tube, as described in connection with FIG.

A high frequency voltage is applied to this electrode by high frequency applying means 3.

The coldest point part 41 of the discharge tube is a place where the strength of the high-frequency electromagnetic field generated by the high-frequency voltage applied to the electrode 2 weakens below the discharge starting strength, and is not affected by the temperature rise of the discharge tube caused by this high-frequency electromagnetic field. It is set away from the light emitting part where the high frequency electromagnetic field is concentrated, and the discharge tube shape is set so that the end of the discharge tube has a narrow diameter (several mm in diameter and 50 to 100 liters in length).
This discharge tube shape is provided as the tip 41 of the protruding portion 4 which is bent into an L-shape and extends to a length of 5 mm, but depending on the installation conditions of the device of the present invention, the shape of the discharge tube is within the range that satisfies the above conditions, for example, from the center of the discharge tube. It is also possible to set the coldest point part in the narrow diameter part extended in a T-shape or in the narrow diameter part bent in a U-shape.

Fluctuations in light intensity due to temperature changes are caused by fluctuations in internal saturated vapor pressure. By providing this coldest point portion, the internal saturated vapor pressure is determined by the coldest point, so fluctuations in the amount of light can be greatly reduced.

A temperature control means 5 is provided at the coldest point of the discharge tube.

The frequency I M applied to the electrode 2 by the high frequency application means 3
Hz ~ 102 MHz, voltage vpp2
The high-frequency electromagnetic field generated by the high-frequency voltage with a duty ratio of 5 to 90% excites the discharge initiator gas atoms such as mercury in the discharge tube, causing ultraviolet rays (mainly 253
．． 7 nm). This ultraviolet light acts on the phosphor coated on the inner wall of the discharge tube, causing it to emit light in the visible light range.

On the other hand, due to the high horse wave electromagnetic field generated by the electrode 2,
When the temperature of the discharge tube and the gas inside the tube rises and the saturated vapor pressure of the discharge initiator gas changes, the amount of ultraviolet light emitted from the discharge initiator gas changes accordingly, and accordingly, the visible light emission from the phosphor also changes. This light intensity change has a convex shape with an apex between 30" and 50°C, and appears as a light intensity change in response to a change in the discharge tube wall temperature. In the area where the high-frequency electromagnetic field is concentrated, the discharge tube outer wall temperature is Depending on the applied voltage, the temperature at the light emitting part where the high-frequency electromagnetic field is concentrated can reach 200°C or more, and for discharge tubes that do not have a coldest point, the amount of light decreases significantly for this reason. In a discharge tube equipped with a There is no fluctuation in the amount of light because it is affected by the point.More preferably, the amount of light can be reduced by keeping the coldest point at a temperature (between 30°C and 50°C) that produces the maximum amount of light emitted. A large amount of stable light can be obtained without any degradation.

In the discharge tube shape of this lighting device, the intensity of the high frequency electromagnetic field generated by the high frequency voltage applied to the electrode 2 is weak at the L-shaped protrusion 4 of the discharge tube, as shown in FIG. Even if a discharge cell having the same shape as the narrow diameter portion of the discharge tube is placed in the area, the inert gas (e.g. Ar) and discharge initiating material (e.g. mercury) with the same composition and pressure as in the discharge tube are placed. The high-frequency electromagnetic field strength in the area becomes lower than the discharge starting strength. Actually, in a discharge tube 1 having a shape as shown in FIG. 1 in which the narrow diameter portion 4 is integrated, the electromagnetic field distribution is affected by the discharge body ions and ionized electrons in the discharge tube due to the discharge in the large diameter portion of the discharge tube. Due to the electrons leaked into the narrow diameter part of the discharge tube, weak light emission is observed in the gas inside the discharge tube. The temperature rise in the light emitting part is extremely small, unlike a discharge that is started and continues to exceed the discharge starting intensity. The light emission in this part is mainly due to the discharge induced by the movement of electrons within the tube, and is caused by a sudden discharge state accompanied by the movement of electrons and ionic gas in the large-diameter portion of the discharge tube, which is exposed to a high-frequency electromagnetic field that exceeds the discharge starting intensity. It is considered that this does not cause a rise in gas temperature. In addition, due to the low thermal conductivity of the material of the discharge tube, the narrow diameter part does not receive heat from the high temperature light emitting part and does not rise in temperature, and the temperature becomes almost the same as the ambient temperature, making the narrow diameter part the lowest temperature part of the discharge. There is. Therefore, by making this part the coldest point part (at a temperature higher than room temperature) and adjusting the temperature, it is possible to adjust and stabilize the amount of light emitted from the discharge tube.

The temperature adjustment at the coldest point is performed by the temperature adjustment means 5.

The configuration of the means is, for example, as shown in FIG. 2, which includes a temperature detecting means 6 such as a thermistor that generates electrical signals in accordance with a plurality of temperatures, and an analog-digital (analog-digital) converter that converts the analog signal from the temperature detecting means into a digital signal. The system comprises A/D) conversion means 7, control means 8, heating means 10 such as a heater, and driving means 9 for driving the heating means. The temperature detection means 6 is installed in a distributed manner in the discharge tube narrow diameter section (coldest point section) 4, and generates an electric signal according to the temperature, and the analog signal is
/ It is converted into a digital signal by the D conversion means 7, and the control means 8 compares the signals from the plurality of digitalized temperature detection means, and selects the one corresponding to the lowest temperature (coldest point temperature), Furthermore, the heating means driving means 9 compares the temperature with a reference temperature that provides the preset maximum amount of light, and outputs a difference value signal to a signal input corresponding to a temperature equal to or higher than the reference temperature.
send to The heating means 10 is installed over the entire coldest point portion and is driven by the driving means 9. The discharge tube wall temperature that provides the vapor pressure of the discharge initiating material to emit light at the maximum amount of light is 30° to 50'C.
(nearly 378C in this embodiment) and is usually higher than room temperature, so cooling to the set temperature is performed by air cooling (heat radiation) in the atmosphere. In this configuration, there is no need for a cooling device because the compulsory cooling is not performed, and even in temperature control, the output factor is small, and the temperature control method is simplified.

In addition, in the above explanation, the reference temperature preset by the control means was set at the temperature at which the maximum amount of light was obtained, but it is also possible to adjust the amount of light by setting the set temperature to a point higher than room temperature. .

FIG. 5 shows a lighting device according to another embodiment of the invention.

The discharge tube 1b is an aperture type having a narrow width in the longitudinal direction and a portion not coated with phosphor to increase the amount of light. It is characterized by being placed outside the metal container and in the open air. The electrodes 2b are formed by winding a conductor wire into a coil shape a plurality of times, and are installed in one or several sets. A high frequency voltage is applied to the electrode 2b by a high frequency applying means similar to that explained in FIG. The high frequency application means is housed in whole or in part within the metal container, but it can also be installed outside the container. The discharge tube emitted light is irradiated to the outside through the metal container window 12.

This configuration is particularly effective because the high frequency electromagnetic field generated near the electrode is blocked by the metal container l1 and does not reach the narrow diameter portion 4 of the discharge tube.

The lowest temperature part of the discharge tube is isolated from the generated high frequency electromagnetic field acting part, and temperature rise due to the high frequency electromagnetic field is further prevented than in the embodiment shown in FIG. In addition, since the thermal connection with the discharge tube light emitting part due to atmospheric flow is also severed, the temperature of the lowest temperature part of the discharge tube is fixed at the external ambient temperature, and the temperature control means is omitted. Adjust the temperature of the temperature section. This configuration shields the high frequency electromagnetic field generated within the metal container, so high frequency noise to the outside is reduced.

The electrode 2b has a smaller width in the longitudinal direction of the discharge tube than the shape 2 in which it is wound around the discharge tube in the longitudinal direction as explained in FIG. At the connection part, the space inside the metal container due to the thickness of the electrode is no longer required, and the small diameter part of the discharge tube is immediately taken out of the container from the large diameter and small diameter connection parts, and the small diameter part of the discharge tube is exposed outside the container. The volume of the diameter portion has increased, and the shape is effective for shielding high-frequency electromagnetic fields and for keeping the narrow diameter portion of the discharge tube in thermal equilibrium with the ambient temperature.

FIG. 6 shows an embodiment of the structure which further includes a temperature control means 5 for the narrow diameter portion of the discharge tube exposed to the outside of the metal container in FIG. In this configuration, compared to the embodiment shown in Fig. 5, it is less affected by changes in external temperature, and compared to the embodiment shown in Fig. 1, the accuracy of temperature control in the narrow diameter portion of the discharge tube is improved. It also has the effect of reducing high frequency noise to the outside.

All of the electrodes in the above embodiments have been explained in terms of electrodes in the form of coiled conductor wires, but electrodes made of metal are installed at both ends of the discharge tube generating section as shown in Fig. 3. The present invention is also effective for lighting devices.

FIG. 7 shows a lighting device with the configuration shown in FIG. 1 and a lighting device with the configuration shown in FIG. 11, in which the coldest point of the discharge tube is located at a location where the high-frequency electromagnetic field intensity is equal to or higher than the discharge starting intensity. It is a graph comparing the tube wall temperature of the discharge tube narrow diameter part. As shown in the graph, the narrow diameter portion located at a location where the intensity of the high frequency electromagnetic field at which the discharge starts as shown in FIG.

FIG. 8 shows changes in the amount of light emitted and the room temperature of the lighting device according to the present invention having the general configuration shown in FIGS. 1 and 6. The amount of light emitted remains constant regardless of changes in room temperature, achieving stable light emission relative to the outside temperature.

In addition, in the lighting device according to the present invention having the schematic configuration shown in FIGS. 1 and 6, FIG. 9 shows the change in light amount when the temperature of the coldest point part of the discharge tube is adjusted to above room temperature. Shown below. Optical fi60 for changes in coldest point temperature 30°C to 90°C
It is now possible to change the temperature over a wide range from % to 100%, and the coldest point temperature can be changed from room temperature (20°C to 30'C).
The effect of controlling the amount of light emitted through the above adjustment has also appeared.

Furthermore, the illumination device having the configuration shown in FIGS. 5 and 6 has the effect of reducing external high frequency noise.

(Effects of the Invention) As described above, the lighting device according to the present invention has the coldest point in the discharge tube, and by providing the coldest point at a location below the discharge start level caused by the high-frequency electromagnetic field, the temperature of the coldest point is There is almost no increase in the amount of light, and there is no fluctuation in light intensity even when the light is turned on for a long period of time. Furthermore, by controlling the coldest point temperature to a constant value, particularly adjusting it to 30° C. to 50° C., which provides good luminous efficiency, it becomes possible to adjust the amount of light emitted and obtain a more stable maximum amount of light.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic configuration of a lighting device according to the present invention, FIG. 2 is a block diagram of a temperature control means of the lighting device of FIG. 1, and FIG. 3 is a diagram to which the present invention is applied. 4 is a schematic diagram of another lighting device to which the present invention is applied; FIG. 5 is a schematic diagram of another lighting device according to the present invention; FIG. 6 is a schematic diagram of another lighting device according to the present invention; , a schematic configuration diagram of still another lighting device according to the present invention; FIG. 7 is a graph showing temperature changes at the coldest point in the lighting device configured as shown in FIG. 1; FIG. Figure 9 is a graph showing the amount of light emitted when the lighting equipment shown in Figures 1 and 5 is used and the temperature outside the equipment is changed. A graph showing the change in the amount of light emitted when the temperature of the lowest temperature part is changed. Figure 10 is a diagram of the configuration of a lighting device that has the narrow diameter part of the discharge tube inside the electrode coil. Figure 11 is a diagram showing the strength of the high-frequency electric field. It is a figure explaining a method. In the figure, ■ is a discharge tube, 2 is an electrode, 3 is a high frequency application means, and 4I is the coldest point.

Claims (1)

[Claims] A discharge tube that emits light by applying a high-frequency electromagnetic field from the outside;
an electrode provided outside the discharge tube for applying high frequency to the discharge tube; a high frequency application means for applying high frequency power to the electrode; a lowest temperature section provided protruding from the discharge tube;
2. A lighting device characterized in that the lowest temperature portion is provided at a location where a high frequency electromagnetic field is below a discharge start level at which discharge is caused by the high frequency electromagnetic field generated from the electrode.